The invention relates to a control unit for controlling the lifting or lowering of a loading platform and/or the pivoting thereof to a vertical position and the back-pivoting of the loading platform to a horizontal position of a loading platform system mounted on vehicles particularly on trucks, which system includes an electromechanical and/or electronic control circuit.
Loading platform systems have been known in various forms for many years. These loading platform systems always include at least one lifting actuator which provides for the lifting and lowering of the platform. In certain embodiments of loading platform systems, which also close a loading bed of a truck, the lifting actuator also includes a pivot actuation arrangement by which the loading platform can be pivoted from a horizontal position in which the lifting and lowering of a load is effected, to the vertical position for closing a loading bed of a vehicle during transport of the load. At the destination, the loading platform is then again pivoted back from the vertical position to a horizontal working position for lifting and lowering the loading platform for performing its functions for which the loading platform is designed.
Other loading platform systems without the need for pivoting the loading platform from a horizontal to a vertical position and vice-versa are the so-called folding loading platforms which, at the end of a lowering or lifting procedure, are folded and pivoted or otherwise moved under the loading bed at the rear end of a vehicle.
The lifting activators and, under certain conditions if needed and available, also the folding actuators of such loading platform systems are generally operated by hydraulic or pneumatically actuated piston cylinder systems, but also lifting actuators and pivot actuators of electromechanical design or respectively, electromechanically operated actuators may be employed.
The control for the operation of the loading platform systems, that is, their lifting, the lowering, the pivoting with their front edge onto a street or similar, the pivoting from the horizontal to the vertical position of the loading platform and vice versa, that is, all the functions, which the loading platform of the loading platform system can perform during its design operation, are essentially initiated or respectively, terminated by a central control unit which is generally mounted on a vehicle in the rear near the loading platform system and which makes it possible for the operator to control the operation by manually actuating switch arrangements on the control unit.
Loading platform systems of the type generally also have, disposed on the platform itself, a plurality of switches, which can be operated by foot. These switches supply their signals to the control unit where they are processed and prepared so as to actuate the lifting and pivoting actuators corresponding to the control actions as desired by operator.
The control unit generally comprises an electromechanical and/or electronic control circuit, which processes the signals of manually operable switch arrangements or, respectively, functional elements and of the foot-operable switches and which supplies them for example to the lifting actuators and, if applicable, also to the tilting actuators in order to operate them. In summary, it may be said that the whole operation of the loading platform system is controlled and monitored by the control unit.
Some of such control units include optically visibly at least one indicating light which however indicates to the operator only that the loading platform system is switched on.
It does not need to be pointed out that such loading platform systems on vehicles are subjected during their normal operation, to rough treatment caused by weather and also by handling. In traffic, such influences are, for example, moisture from snow, mist, dust and other soilings, carbon suds and exhaust gases from motor vehicles, but also detrimental influences by inappropriate treatment of the control unit by the operator. Up to now, if the control unit failed as a result of such influences, failures in the loading platform system, particularly the control system, could be determined by relatively simple measures by measuring, for example, the signals and voltages and currents, and faulty components could then be rapidly replaced. In this way, however, the basic problems that cause the failure could not be eliminated. So, it was decided to encapsulate the whole mechanical and/or electronic control system in the control unit in plastic. This technique of course has the advantage that the external conditions described earlier no longer influence directly the control circuit with the switch elements. However, this technique also has the disadvantage that, upon occurrence of malfunctions in the platform loading system, the encapsulated electromechanical and/or electronic control unit does not permit identification of faulty components by measuring procedures and subsequent replacement of faulty components in the control unit or corresponding functional elements of the loading platform system. The advantage of encapsulating the control circuit in plastic therefore has the disadvantage as described above, which is not acceptable for safety and expense reasons, since now, the whole control unit must be removed and replaced by a new unit when a malfunctioning is noticed. The situation is not acceptable for safety reasons since the likelihood of an accident is substantially increased if the operator assumes that the loading platform system including the control unit is operative, but this is actually not the case because a fault in the system cannot be recognized.
It is the object of the present invention to provide a control system for a loading platform, which, even for control units which are partially or fully encapsulated in plastic, provides a minimum of information concerning the state of operation of the loading platform system to the operator so that, based on the information obtained, the operator can start, continue, or discontinue operation of the loading platform system, or not initiate operation in the first place. The control unit should be relatively simple, reliable, and inexpensive.